1. Technical Field
The present invention relates to solder bump structures in flip-chip technologies, and more specifically, to solder bump structures that facilitate good bonding of a chip to a package/substrate.
2. Related Art
In flip-chip technologies, solder bumps are typically formed on top of a semiconductor chip (i.e., integrated circuit IC). Each solder bump is formed directly on an aluminum bond pad of the chip. The chip is then flipped face down and then aligned to a package/substrate. The solder bumps are bonded directly, simultaneously, and one-to-one to the pads of the package/substrate (called package/substrate pads). After that, an adhesive underfill material is used to fill the empty space between the chip and the package/substrate. Once in place, the adhesive underfill material is cured at a high temperature so as to become a solid underfill layer tightly bonding the chip to the package/substrate. The quality of the chip depends in part on the quality of the bonding of the chip to the package/substrate.
Therefore, there is a need for a solder bump structure that facilitates good bonding of a chip to a package/substrate.